How big is this lake? I am guessing that you dammed off a valley and your thoughts of the leak is passing through your dam?

Here in Ontario I have seen some very very odd things with ground water. The rule of thumb here is it will follow the lay of the land. Most really good wells are on top of hills. Long story long if you didn't strip all the top soil from the lake bed and see any wet spots the dam most likely is the problem. These soft spots will transpire water up hill away from the pond area. It is the strangest thing and I for one would never believe it until I seen it.

My thoughts are that if the lake is big enough like 10+ acres I would be just happy I have water that stays.

Cheers Don.

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7/8th of an acre, Perch only pond, Ontario, Canada.